In cellular mobile networks, it is known for the network to be comprised of a network core and a radio access network of cellular base stations known as eNodeBs. User Entities (UEs) such as mobile phones and cellular network enabled computers belonging to subscribers of the cellular network wirelessly connect to an eNodeB for communication with the other subscribers of the cellular network and subscribers of other cellular networks for voice calls, Short Message Service (SMS) exchange and data sessions.
To facilitate communicate with other cellular networks, the network core includes packet data gateways (PDWs) for routing data between subscribers and correspondent nodes located on different external networks. These external networks include the Internet and also the GPRS Roaming Exchange (GRX) network which allows for a dedicated interconnect network between MNO cellular networks.
Roaming
In general, a UE will connect to the cellular network to which it is a subscriber, hereinafter referred to as a home cellular network, for voice and data connectivity. However, this connectivity is limited to the geographic area covered by the home cellular network's radio access network of eNodeBs. Roaming is a term used to describe a scenario whereby a UE connects to a different cellular network in order to receive voice and data connectivity where the home cellular network has no presence. The most common example of roaming is where the UE is located in a different country and there are commercial agreements in place between the local cellular network and the home cellular network with regards to network access and pricing.
The GRX network is used to link the cellular networks in different countries together so that a roaming UE can continue to have network connectivity albeit at a different pricing model. In general, authentication is carried out via a C7 network and data is tunneled between the UE and its home cellular network via the GRX using data tunnels.
There are numerous advantages for a Mobile Network Operator (MNO) of a cellular network to use GRX:                Only one commercial agreement, namely between the MNO and the GRX provider        Each MNO only needs to provision a secure interconnect from their core network to the GRX;        The GRX provides a secure, private and QoS enabled network; and        Only one organization is needed to deal with billing and accounting.        
Without the GRX, each MNO would need to setup commercial and physical arrangements with each foreign operator that is enabled for roaming.
Wi-Fi Wireless Local Area Networks (WLANs) and Hotspot Networks
Wireless local area networks (WLAN) are type of non-cellular wireless data connectivity technology in common use. The IEEE 802.11 family of standards, commonly known as Wi-Fi™ define the operation of WLANs.
A WLAN is generated by a wireless access point (WAP) operating in the 2.4 Ghz and 5 Ghz frequency range. The WLAN enables data connectivity to WLAN devices having a suitable wireless network adaptor card. Due to transmission power constraints, WLANs generally only extend for tens of meters from the WAP.
Although a single WLAN of a WAP only provides a limited range of connectivity, it is possible to extend the reach of a particular Wi-Fi based network by forming clusters of WAPs managed by a network core resulting in what is known as a hotspot network. In a hotspot network many hundreds of short range WAPs can be located over a geographical area and all configured to present the same wireless network name known as a Service Set Identifier (SSID). The plurality of wireless access points are connected to a network core which handles authentication and data transfer so that a hotspot network user has mobility within the hotspot network. Authentication to the hotspot network can be provided using a username and password login. An example of a WiFi Operator (WFO) is British Telecommunications plc in the UK which operates a hotspot network currently known as BT WiFi™.
Most UEs of a cellular network also have WLAN interfaces in addition to their cellular network interfaces and in general the UE preference is to use WLANs where available. From a user perspective, WLAN access is beneficial because cellular network access is normally provided with tiered monthly data allowances and once the allowance, e.g. 1 GB is used up, data is charged per megabyte which becomes expensive. In general, WLAN data access is uncapped and in some circumstances can provide faster data speeds. From an MNO perspective, WiFi Offload is desirable because it reduces the burden on the cellular network.
It is known for MNOs and WFOs to have commercial agreements so that cellular subscribers can access a hotspot network as part of their cellular subscription package with their home network. This is sometimes implemented by assigning the subscriber of the cellular network a set of login credentials to the partner hotspot network.
To improve the hotspot access for a UE, it is also known to automate the authentication in accordance with variants of the Extensible Authentication Protocol (EAP). For example, EAP-TLS uses certificates installed on the UE to authenticate access while EAP-SIM uses a SIM card present in the UE to authenticate. Both methods do not require user interaction to join a hotspot network.
When a subscriber of a cellular network is abroad and therefore cannot use their UE to connect to the radio access network of their home cellular network, prior established roaming agreements between MNOs will allow their cellular device to have the option to roam onto a local cellular network over the GRX. However, roaming to a visitor cellular network, i.e. any cellular network which is not the UE's home cellular network, is regarded as being expensive due to high termination charges. The potential for shock high bills, in particular those incurred by data roaming, can often lead to many users opting to switch off their UEs completely or only allowing voice roaming. In general users prefer to connect to free or cheap WLANs available for example at hotels or cafes. This loss of convenience and functionality to access data and subsequent reduction in quality of experience is considered a necessary compromise to avoid large overseas data charges. However, this can cause a different set of problems in relation to data security and setup issues.
In addition to the roaming agreements under the GRX, MNOs have therefore turned to roaming agreements with overseas WFOs to allow their subscribers to use roaming data more freely. More importantly, the data is often tunneled back to the UE's home cellular network so that the MNO can continue to learn about the user's usage patterns and also control how information is gathered and presented to a subscriber. For example, web pages would be displayed in the user's home language and not the local language.
In a similar manner to the reasons for GRX, as the number of hotspot networks increases, it is a burden to create bilateral agreements across many different countries and hotspots. To address this issue, a roaming service such as the BT WiFi Roam™ is a known platform for allowing UEs to connect to hotspot networks using EAP SIM and other non-SIM based authentication methods as credentials.
A roaming hub interconnect has interfaces to communicate with the hotspot networks and also a number of cellular network facing interfaces. The hotspot networks can be regarded as further radio access networks of the home cellular network when the UE is roaming.
While the purpose of the roaming hub interconnect is to connect networks, due to commercial or political considerations, there may be reasons for not allowing subscribers of a particular cellular network to connect to a particular hotspot network. Each cellular and hotspot network is therefore configured manually to specify an access list, typically in the form of a white list or blacklist of allowable or rejected networks respectively.
A problem with this approach is that the blacklists are generally static and therefore there will be problems arising from data staleness resulting in UEs not being able to connect to newly added networks and blacklisting networks in response to a commercial or political situation.